The present invention relates to an optical moisture sensor. More particularly, the present invention relates to a self-contained optical moisture sensor suitable for a wide variety of non-vehicular applications.
Rain sensors for use in vehicular applications are well known. Rain and moisture sensors for various non-vehicular applications are also known in the patent literature, for example:
U.S. Pat. No. 3,705,533 describes a precipitation sensor having two buckets secured to each other for tilting movement between two end positions, is provided with a precipitation collecting and distributing means which collects precipitation during tilting of the buckets and has a normally closed valve operated by the buckets to open when the same are in the end positions so that the collected precipitation is alternately discharged into the buckets. Evaporation retarding covers with small inlet cutouts close the tops of the buckets without bouncing back, and magnetic switch means generate a counting pulse for each tilting movement.
U.S. Pat. No. 3,808,385 describes a moisture responsive actuator for controlling the operation of a fluid operated sprinkling system, irrigation system or the like. The moisture responsive actuator is provided with hygoscopic material which expands in response to contact with rain water to depress a switch to deactivate the sprinkling system, the hygroscopic material contracting upon drying to release the switch, whereupon the sprinkling system is activated.
U.S. Pat. No. 5,796,106 describes a detector for detecting the presence of ice, water, mist, frost or other solids or liquids on a sensing surface. The sensing surface is a medium substantially transparent to electromagnetic radiation and solids or liquids are deposited on such sensing surface. A transmitter directs radiation onto the sensing surface and a receiver is responsive to radiation reflected from the surface. A discriminator circuit receives an output from the receiver and provides an output indicative of whether a solid or liquid is present on the surface.
U.S. Pat. No. 5,836,339 describes a raindrop counter and control system for irrigation systems which is said to provide for quick detection of the presence and subsequent absence of precipitation once it has first been detected. The counter and control system disables normal operation of, for example, automatic irrigation systems by interrupting power to the irrigation valves during and after detection of precipitation. Various features including sensitivity selections and varied delay periods are also described. The apparatus includes a small outdoor probe, and a separate control and display unit for interacting with a plurality of automated systems.
Notwithstanding the efforts noted above, moisture sensing in a number of non-vehicular applications could clearly benefit from an improved moisture sensor. For example, self-closing skylights and windows exist, but are relatively rare because of the lack of sufficiently sensitive moisture sensors. Condensation sensing in heating, cooling and ventilation systems is rarely done, because no currently available sensor is sufficiently reliable. Remote meteorological stations are in use, but require maintenance for the tipping bucket rain gauge. Accurate recording of moisture in desert environments does not occur because available sensor systems are not sufficiently sensitive.
Accordingly, what is needed is an optical moisture sensor which is versatile, rugged, provides a sizeable sensed area so as to be sensitive to extremes, high and low, of humidity and precipitation events, is low maintenance, and low in cost.